Category Archives: Bacillus

You know the symptoms well enough. The clammy chill that washes over your body, the clenching in your stomach and then, finally, the dash to the bathroom, possibly accompanied by a split-second decision about which part of your body to aim at the toilet first.

A team from the Australian National University looked at the way the body responds to the bacteria Bacillus cereus, which can cause food poisoning and sometimes lead to serious infections elsewhere in the body, including sepsis, pneumonia and meningitis.

They found a toxin secreted by the bacteria binds directly to cells in the human body and punches holes in the cells to kill them, triggering an immune response.

Abstract

This study was conducted to investigate the presence of Bacillus cereus in ice cream samples and to identify associated toxin genes by mPCR. 125 ice cream samples were used as material. A total of 38 samples were found to be positive for B. cereus. It was found that 31.9% of the isolates had three enterotoxic HBL complex encoding genes, 10.6% had two hbl genes and 6.3% contained one hbl gene. On the other hand, 15.9% of the isolates contained three NHE complex encoding genes, 31.9% had two nhe genes and 20.2% contained one nhe gene. Also 7.4% of isolates were found to contain both NHE and HBL complexes while ctyK1 was not detected from any isolate. The presence of B. cereus and their enterotoxigenic genes in ice creams may be a potential risk for public health.

Practical applications

The presence of the B.cereus in high numbers and the toxins in foods pose a potential risk in terms of health and food spoilage. In food poisoning cases, hbl, nhe, cytK, and the effect of emetic toxin are especially notable. The resistance of spores against pasteurization and psychrotolerant feature enable the explanation of the existence of B. cereus in ice‐cream.

The Centre for Food Safety (CFS) of the Food and Environmental Hygiene Department today (November 26) announced the test results of a recently completed seasonal food surveillance project on the microbiological quality of poon choi. Thirty samples were collected and all passed the tests.

A CFS spokesman said, “As poon choi is popular for gatherings during winter and there were previous cases of bacterial food poisoning associated with poon choi, the CFS has continued to conduct a seasonal food surveillance project this year to assess the microbiological quality of poon choi. A total of 30 poon choi samples were collected from different retailers (including online retailers) for testing of common food poisoning organisms including Bacillus cereus, Clostridium perfringens, Salmonella, coagulase-positive staphylococci organisms and Vibrio parahaemolyticus.”

Despite the satisfactory results of all samples tested, the spokesman reminded people to be careful when purchasing and enjoying this seasonal delicacy. He advised consumers to order poon choi from licensed and reliable shops, avoid prolonged storage of poon choi at room temperature to reduce the risk of bacteria growth, reheat poon choi thoroughly before consumption, consume cooked or reheated poon choi as soon as possible or keep the food at temperatures above 60 degrees Celsius, and stop consuming the food if it tastes or smells abnormal.

“The public should also maintain a balanced diet and avoid eating too much food with high levels of energy, sugar, salt or fat,” the spokesman said.

He also appealed to the food trade not to entertain orders beyond handling capacity. Traders are reminded to check the quality of food and ingredients when they are delivered to them. In addition, to reduce the risk of food poisoning, they should avoid preparing food too far in advance and take note of the temperature in storing, transporting and preparing food.

“All food and food ingredients should be stored at safe temperatures while perishable items should be stored at 4 degrees C or below. The cooling time of cooked food should be reduced as far as possible, for example, by dividing food into smaller portions or placing it in shallow containers. When transporting hot poon choi, it should be kept at above 60 degrees C, and for chilled poon choi, it should be kept at 4 degrees C or below,” the spokesman said.

“Traders should also provide clear advice on the proper methods of storing and reheating of poon choi to consumers so as to further reduce the risk of food poisoning due to improper handling,” he added.

The CFS will continue its surveillance of poon choi available in the market to ensure food safety and protect the health of the public.

Abstract

As the most cost‐effective tool to ensure microbial safety, thermal processing induces a large portion of sublethal injury presenting a potential hazard to food safety. Thermal treatment at 63 °C for 1 min injured 2.22 log cfu/ml totally, half of which were sublethally injured using plate counting method. After 2 min, the inactivation log of Bacillus cereus reached 1.55 while the sublethally injured log even reached 2.16. As for the sublethally injured rate of the B. cereus, it was over 65% after 0.5 min and kept ever‐increase with time. In the end, the injured rate arrived at 99.30% after 2 min processing time. Partial esterase enzyme inactivation was found after 0.5 min heat treatment with flow cytometry combining carboxyfluorescein diacetate/propidium iodide (PI) double‐staining, but B. cereus was not dyed by PI at 63 °C. Comparing with the initial protein concentration of 0.57 ± 0.02 μg/ml, the leakage of the protein was not so notable though the general trend was increasing with duration of heat. Scanning and transmission electron microscopy analysis revealed that a portion of cells morphology and structure had changed after thermal process.

Practical applications

Bacillus cereus is an endospore forming pathogenic, causing foodborne illnesses and outbreaks all over the world. This research indicated that thermal treatment at 63 °C was a sublethal stress for B. cereus that a portion of cells were sublethally injured which could resume growth in suitable condition and might exist potential safety hazard if used for food pasteurization.